Roger Stuart Harker was born in Grassington, Yorkshire, England in June 1942, the son of Edith Leach and Arthur Cecil Harker. As a schoolboy, Roger was a member of the Wharfedale Fell Rescue Organisation, and later became a founding member of the Northern Cavern and Mines Research Group. He attended the University of Leicester from 1961 to 1964, graduating with a degree in Geology. He then took a position in the Surveyor's Department at the Geevor tin mine, at Pendeen, in Cornwall, and later with Consolidated Goldfields, in Scotland.

In 1966, Roger returned to the University of Leicester and began his graduate studies, receiving his PhD in 1971. He opened a mineral shop called “Lythe Minerals” and in 1970 married Susan D. P. Groves. In 1973 he and Susan moved to Rothley, a village five miles north of Leicester, where their children Rachel and James were born.

Roger became a member and regular lecturer at meetings of the Russell Society, and an enthusiastic field leader -- often to the Grassington Moor and Greenhow Mining Fields in his native Yorkshire, where his knowledge of local mining history and industrial archaeology were expertly blended with geology and mineralogy.

Many people who went on to become members of the Russell Society were first introduced to mineralogy either as casual, inquisitive visitors to Lythe Minerals in Oxford Street, Leicester, or as pupils at Roger's evening classes at Leicester, Derby and Nottingham.

He died on March 15, 1983, at the age of 40, at his home in Rothley, Leicestershire.